Duplex scanning exploration of the ophthalmic artery for the detection of the hemodynamically significant ICA stenosis

Evolution of the Flow Patterns After Endovascular Treatment in Patients with High-Grade Carotid Artery Stenosis - the Clinical Value of Insonation of the Supratrochlear Artery and Alternating Flow

AIM

We aimed to describe the evolution of flow pattern in the ophthalmic artery (OA) and supratrochlear artery (SA) by transcranial Doppler (TCD) ipsilateral to a severe proximal carotid artery stenosis before and after staged endovascular treatment (EVT).

METHODS

We insonated and recorded the flow patterns of OA and SA in 63 patients with ≥ 80% carotid artery stenosis before and after staged carotid angioplasty and stenting at 2-4 weeks apart. Based on the direction of OA and SA blood flow, we categorized patients into (1) reversed, (2) alternating, or (3) forward flow, groups. We evaluated the evolving sonographic flow patterns in OA and SA at the 3-time points and correlated them with the stenotic and flow velocity change.

RESULTS

Despite the disconcordance between OA and SA, the evolution of flow direction were evoluted from reversed to alternating or from alternating to forward in both OA and SA. OA and SA's disagreement rate at three-time points was 19.1%, 49.2%, and 28.6%, respectively. After angioplasty alone, we detected an alternating flow in 21 (33.3%) and 46 (73.0%) patients in OA and SA, respectively. Alternating flow patterns in SA persisted in 20 patients (31.7%) after stenting. The post-angioplasty residual stenosis did not differ between the three flow pattern groups (p>0.05).

CONCLUSIONS

An alternating flow in OA or SA might mark the hemodynamic recovery after EVT. Insonation of SA may provide supporting evidence for hemodynamic change in patients with carotid artery stenosis undergoing EVT.

Carotid artery stenting improves cerebral hemodynamics regardless of the flow direction of ophthalmic artery

We enrolled 221 patients with elective carotid artery stenting (CAS). Patients with contralateral carotid stenosis exceeding 50%, insufficient vertebral artery (VA) flows, or angioplasty at subclavian artery were excluded. All patients underwent serial cerebral ultrasound studies. Of the 116 included patients, the direction of ophthalmic artery (OA) flow was forward in 74 patients while reversed in 42. The reversed flow group had worse ipsilateral stenosis, higher hemoglobin, and cardiac output. After CAS, the reversed flow group had an immediate recovery of ipsilateral internal carotid artery flow volume (FV; P < .0001), time average velocity (TAV) of middle cerebral artery (P = .02), and normalization of OA flow. The forward flow group had gradual decrement in TAV of contralateral anterior cerebral artery (P = .01) and total FV of VA (P = .001). Our results suggest CAS improves cerebral hemodynamics through different ways regardless of the direction of OA flow.

Transcranial duplex ultrasound of the ophthalmic artery

The purpose of this study was to identify the ophthalmic artery (OA) by means of transcranial color-coded sonography using a new approach via the transtemporal bone window and to compare blood flow measurements with values obtained from the transorbital approach. A total of 105 subjects were included. Two individuals had an insufficient unilateral bone window, according to our inclusion criteria. Of the remaining 208 OAs, 206 (99%) could successfully be insonated via the transorbital approach and 190 (91%) via the transtemporal approach. Transorbital systolic and diastolic flow velocity (FVs) ranged between 15 and 67 cm/s (mean +/- SD: 35 +/- 10) and 4 to 36 cm/s (14 +/- 5), pulsatility index ranged between 0.4 to 2.8 (1.2 +/- 0.4). Transtemporal systolic and diastolic FVs ranged between 15 and 58 cm/s (33 +/- 9) and 4 to 25 cm/s (11 +/- 4). Transorbital and transtemporal FVs correlated significantly (p = 0.01). Our study demonstrates that transtemporal insonation of the proximal intracranial OA is feasible. Whenever OA assessment for analysis of collateral function is required, this simple approach, avoiding direct eye bulb insonation, should be considered.

Assessment of ophthalmic artery collateral pathway in the hemispheric cerebral hemodynamics in patients with severe unilateral carotid stenosis

The role of ophthalmic artery collateral pathway in hemispheric hemodynamics in patients with severe carotid stenosis is controversial. The aim of the present study was to address this question comparing the asymmetry of the velocity in middle and anterior cerebral arteries (MCAs and ACAs) and cerebrovascular reactivity (CVR) in MCA on stenotic side in the patients with unilateral severe stenosis of internal carotid artery (ICA) in patients with and without ophthalmic artery collateral pathway. The cohort of 118 patients with carotid stenosis was prospectively assembled. Fifty patients who had severe unilateral ICA stenosis (71%-99%) by Duplex Ultrasound (DUS) were observed by transcranial Doppler (TCD). Cerebral blood flow velocity in MCA and ACA in both sides, direction of blood flow in ophthalmic artery (OA) and CVR on the side of stenosis were determined. There were 14 patients with retrograde blood flow in OA (Group I). The remaining 36 patients with anterograde flow in OA composed Group II. The degree of interarterial asymmetry of peak and mean velocity (Vpeak and Vmean) in MCA and ACA and CVR in MCA were compared in both groups. The degree of ACA asymmetry by Vpeak was 44.0% +/- 6.9% in Group I and 38.3% +/- 3.9% in Group II (p = 0.49), by Vmean 40.3% +/- 6.7% and 36.6% +/- 3.8% (p = 0.63) respectively. The degree of MCA asymmetry by Vpeak was 24.2% +/- 2.8% in Group I and 19.5% +/- 5.0% in Group II (p = 0.42), by Vmean 23.5% +/- 2.9% and 20.6% +/- 5.1% (p = 0.63) respectively. CVR in Group I was 26.1% +/- 6.1%, in Group II 29.0% +/- 6.7% (p = 0.65). The ophthalmic collateral pathway has no influence on hemispheric cerebral hemodynamics in patients with severe unilateral carotid stenosis.

Ophthalmic artery flow direction on color flow duplex imaging is highly specific for severe carotid stenosis

BACKGROUND/PURPOSE

Collateral flow patterns are important risk factors for brain ischemia in the presence of internal carotid artery (ICA) stenosis or occlusion. Ophthalmic artery (OA) flow reversal, routinely studied by transcranial Doppler sonography, is an important marker for high-grade ICA stenosis or occlusion. The authors sought to define the value of assessing OA flow direction with color flow duplex ultrasonography (CDUS) in the setting of significant ICA disease.

METHODS

Of all patients having routine carotid ultrasound in the neurosonology laboratory between July 1995 and November 2000, 152 had both carotid and orbital (OA flow direction by reduced power orbital CDUS) examinations as well as angiographic confirmation of stenosis to which North American Symptomatic Carotid Endarterectomy Trial criteria could be applied. Degree of angiographic stenosis in these 152 patients (304 arteries) was correlated with OA flow direction.

RESULTS

Of 304 arteries, 101 had greater than 80% stenosis by angiogram. In 56 of these 101 arteries with high-grade stenosis or occlusion, the ipsilateral OA was reversed; however, OA flow direction was never reversed ipsilateral to arteries with less than 80% stenosis (sensitivity 55%, specificity 100%, negative predictive value 82%, and positive predictive value 100% for OA flow reversal as a marker of high-grade carotid lesions).

DISCUSSION/CONCLUSIONS

OA flow direction is easily studied with CDUS. Reversed OA flow direction is highly specific (100%) for severe ipsilateral ICA stenosis or occlusion, with excellent positive predictive value, moderate negative predictive value, and limited sensitivity. OA flow reversal is not only quite specific for severe ICA disease, which may be helpful if the carotid CDUS is difficult or inadequate, but may also provide additional hemodynamic insights (i.e., the inadequacy of other collateral channels such as the anterior communicating artery). OA evaluation can provide important hemodynamic information and should be included as part of carotid CDUS if there is any evidence of ICA stenosis or occlusion.